Front Cover: The First Total Synthesis of Racemic Chebulic Acid (Eur. J. Org. Chem. 6/2022)

Abstract

The Front Cover shows a branch and some fruits of Terminalia chebula, a tropical tree. Chebulic acid (the formula in the magnifying glass) is the aglycon of several antioxidant ingredients of the fruit. The artwork is based on a graphic from 1874 (reproduced from www.biolib.de published by Kurt Stüber). The first total synthesis of chebulic acid was accomplished. Key steps were a cerium‐catalyzed α‐hydroxylation of an β‐oxoester and a cyanide‐catalyzed ring‐transformation of the respective intermediate product to the δ‐lactone structure. More information can be found in the Research Article by D. Kieslich and J. Christoffers.

Synthetic Studies towards Pheromones by Cyanide‐Catalyzed Ring Transformation of α‐Hydroxy‐β‐oxoesters to δ‐Valerolactones

“… [17] For a detailed mechanistic proposal of this ring transformation please see Scheme 4 and related text below. Based on this discovery, we have recently been able to perform the first total synthesis of chebulic acid ( 5 ) [18] . Thus, we envisioned the synthesis of pheromones 3 and 4 a via lactone 9 a by reconstruction of the side chain.…”

“…Based on this discovery, we have recently been able to perform the first total synthesis of chebulic acid (5). [18] Thus, we envisioned the synthesis of pheromones 3 and 4 a via lactone 9 a by reconstruction of the side chain. Compounds 3 [4] and 4 a [6] had been prepared before, even in enantioselective fashion, while we report herein the synthesis of racemates.…”

“…13C{ 1 H} NMR (125 MHz, CDCl 3 ), 16 a: δ = 14.21 (CH 3 ),18.61 (CH 2 ), 22.79 (CH 2 ), 24.43 (CH 2 ), 26.87 (CH 2 ), 29.17 (CH 2 ), 29.43 (CH 2 ), 29.56 (CH 2 ), 29.68 (2 × CH 2 ), 29.84 (CH 2 ), 32.02 (CH 2 ), 33.59 (CH 2 ), 63.42 (CH), 81.54 (CH), 170.70 (C) ppm; 16 b: δ = 14.21 (CH 3 ),18.31 (CH 2 ), 22.79 (CH 2 ), 24.20 (CH 2 ), 26.34 (CH 2 ), 29.15 (CH 2 ), 29.43 (CH 2 ), 29.56 (CH 2 ), 29.66 (2 × CH 2 ), 29.81 (CH 2 ), 32.02 (CH 2 ), 33.87 (CH 2 ), 64.13 (CH 2 ), 82.05 (CH), 170.61 (C) ppm. IR (ATR): 2954 (w), 2924 (vs), 2854 (m), 1743 (s), 1237 (m) cm À 1 .…”